In an era where water scarcity is becoming increasingly severe, the search for clean water sources has become a top priority. Recently, American scientists have developed an ultrasonic water collection device that can release usable water in just a few minutes when exposed to sunlight. This groundbreaking technology holds promise for breathing new life into communities suffering from a lack of freshwater resources.
Over the past few years, researchers have developed a series of sponge-like materials that make it possible to collect water from the atmosphere, as even in extremely dry areas, the air contains small amounts of water. However, traditional methods typically require heating to extract water and involve longer waiting times.
To address this challenge, engineers from the Massachusetts Institute of Technology (MIT) in the United States have developed a new device that does not rely on solar heating and can quickly recover water. They use ultrasonic vibrations in an atmospheric water harvester to “shake out” the water from the absorbent material. This research was published in the journal “Nature” in November and has garnered attention from over 20 mainstream media outlets with nearly 10,000 views.
The research team has long been dedicated to developing materials that interact with environmental conditions and aims to provide reliable drinking water sources for regions lacking both freshwater and seawater resources. In the process, they explored Atmospheric Water Harvesting (AWH) technology and engineering design, enabling materials to efficiently absorb water from the air.
Initially, like other teams, they thought that an AWH system placed outdoors would absorb water at night and release condensed water during the day with the help of sunlight, but the results were not satisfactory.
Dr. Svetlana Boriskina, Chief Research Scientist in the Mechanical Engineering Department at MIT, explained to the MIT News Office, “Materials that are good at absorbing water are often reluctant to release it. It often takes a significant amount of energy and time to extract water from the material.”
A turning point came when graduate student Ikra Iftekhar Shuvo, with a background in wearable medical devices, joined the team. They believed that ultrasonic waves at the right frequency might solve the challenge of water-absorbing materials being reluctant to release water.
Ultrasonic waves refer to sound pressure waves with frequencies exceeding 20 kilohertz (20,000 times per second), which are invisible and inaudible to humans.
The research team specifically designed an ultrasonic actuator, featuring a flat piezoelectric ceramic ring (PZT) that generates slight vibrations when voltage is applied. The outer ring of PZT surrounds another ring with tiny nozzles, and when water droplets vibrate, they fall from the nozzles into upper and lower collection containers.
They placed the high-frequency ultrasonic device above PAM-LiCl hydrogel that absorbed water from the air. Once sufficient water was absorbed, the high-frequency ultrasonic actuator was activated to break the bond between water molecules and the material, allowing water droplets to be released smoothly into the collection containers.
Multiple tests showed that the water production rate per cubic meter of hydrogel material could reach 3.25 liters per day with extremely low energy consumption (average of 0.576 MJ/kg). The test device could also increase water production efficiency by over 5 times (16.25 liters) through continuous vertical stacking, significantly boosting water output.
Researchers stated that the cost of water collected in this way is $0.19 per liter, far lower than bottled water in countries like the United States, the United Kingdom, Canada, and Australia, showing immense commercial potential. Due to the low cost of hydrogels, their lifespan has a limited impact on water costs.
Moreover, the device does not rely on thermal energy and can be powered by small solar panels, utilizing solar cells as sensors that automatically activate the ultrasonic water release mode once the material reaches saturation.
The research team also mentioned that while hydrogels were used in the experiments as a demonstration, this technology is highly versatile and could be applied to metal-organic frameworks (MOFs), superabsorbent fibers and textiles, salts, desiccants, and other adsorbents with just a simple evaluation.
Boriskina explained, “In the past, people have been searching for ways to collect usable water from the atmosphere, which is crucial for desert areas or regions where even seawater desalination is not an option. Now, we have this efficient method for quickly recovering water.”
She envisioned a future household water vapor collection system composed of a fast-acting moisture-absorbing material and an ultrasonic actuator powered by solar energy for fully automatic operation. When the absorbent material becomes saturated, the ultrasonic actuator would release the water vapor, ultimately transforming it into a sustainable and consistent source of drinking water.
She further stated, “The beauty of this device lies in its complete versatility, as it can be used with almost any absorbent material. With this ultrasonic water collection device, we can now extract the water we need daily through a repetitive cycle.”
This work was partially carried out at the MIT.nano and ISN facilities at the Massachusetts Institute of Technology, and received support from the Abdul Latif Jameel Water and Food Systems Lab at MIT and the MIT-Israel Zuckerman STEM Fund.